1. Field of the Invention
The present invention relates to a data input device for an electronic instrument and a method of entering data, and more particularly to a technique for preventing an incorrect data entry in a data input device provided with an electrostatic capacitance type touch sensor as well as in a data entry method using such a data input device.
2. Description of the Related Art
In a traditional data input device for an electronic instrument, a data input operation by an operator is sensed by means of an electrostatic capacitance type touch sensor. Such a data input device includes a data input operation surface located at the top thereof and having a flat plane and is advantageous in enabling a highly sensitive sensing of data entered and at the same time presenting a high degree of both functionality and aesthetic appearance. Consequently, in recent years, such a data input device is used widely more and more for various kinds of electronic instruments.
In the data input device described above, a plurality of segments are provided on the data input operation surface so as to correspond to a plurality of key switches (hereinafter, the segments are referred to simply as “key switches” as appropriate), wherein when the fingers of an operator touch the key switches on the data input operation surface, the touching operation on the key switches is sensed whereby the output data corresponding to the key switches are sent to an electronic instrument. In such a data input device as described above, however, a key switch which the operator does not intend to touch may be accidentally touched as shown in FIG. 11, thus causing an incorrect data entry.
A data input device shown in FIG. 11 includes a touch sensor system which includes touch sensors 101, 102 and 103 corresponding respectively to three key switches and a data sensing circuit 106 to sense the electrostatic capacitance variation of the touch sensors 101, 102 and 103. In this connection, the touch sensors 101, 102 and 103 may be disposed on the lower or upper side of a data input operation surface (not shown) which is provided with the key switches.
In FIG. 11, it is assumed that the operator puts a finger 105 in touch with a relevant part on the data input operation surface so as to implement a data input operation only to a key switch which corresponds to the touch sensor 101. Under the circumstance described above, however, it can possibly happen that depending on the sensitivity of the touch sensor system, the data input operation is wrongly interpreted (despite the intention of the operator) as being implemented also to a key switch which corresponds to another touch sensor (for example, the touch sensor 102) and close to which the finger 105 is put. Or, it is possible that when the operator intends to implement a data input operation to a given key switch using the finger 105, a portion of the body of the operator other than the finger 105 (for example, another finger, a palm, or the like) touches an unintended key switch, thus causing an incorrect data entry.
In order to prevent such an incorrect data entry, a method is conventionally proposed in which assuming the finger position of the operator for implementing a data input operation, the priority order of the key switch operation for entering data is previously set up in accordance with the order of the likelihood of the data input operation to be practically implemented, wherein when a signal indicating data input operations for a plurality of key switches is sensed by the touch sensor system, it is determined that only a data input operation for the key switch, to which the top priority is assigned, is executed (refer to, for example, Japanese Patent Application Laid-Open No. 2007-317201).
The method described in Japanese Patent Application Laid-Open No. 2007-317201 is premised on that the operator conducts a data input operation with one finger (for example, an index finger or a thumb) so as not to touch two or more key switches at the same time in the normal operation. Accordingly, the method can be appropriately applied only to a data input device which is provided with a relatively small number of key switches, for example, an operation panel for a remote control and a home electric appliance.
On the other hand, in the case of a data input device (for example, a keyboard for a personal computer) which is provided with a relatively large number of key switches and in which the operator is supposed to implement a data input operation with a plurality of fingers (usually, fingers of the both hands) at a high speed, it is also strongly desired in view of operability that the operator is allowed to intentionally implement a data input operation to two or more key switches at the same time while an incorrect data entry can be prevented as described above. However, the method described in Japanese Patent Application Laid-Open No. 2007-317201, when applied for use in the data input device with a relatively large number of key switches, does not enable prevention of an incorrect data entry while maintaining the desired operability.